CPC G06V 40/1306 (2022.01) [G06F 21/32 (2013.01); H03H 9/17 (2013.01)] | 20 Claims |
1. An apparatus, comprising:
an ultrasonic sensor stack; and
an acoustic resonator, comprising:
a first higher-impedance layer;
a second higher-impedance layer; and
one or more low-impedance layers residing between the first higher-impedance layer and the second higher-impedance layer, each of the one or more low-impedance layers having a lower acoustic impedance than an acoustic impedance of the first higher-impedance layer or an acoustic impedance of the second higher-impedance layer, at least one of the one or more low-impedance layers having a thickness corresponding to a multiple of a quarter wavelength at a peak frequency of the acoustic resonator.
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